Automatic device for controlling catalytic mufflers

ABSTRACT

A device for automatically controlling a by-pass electro-valve of a catalytic muffler comprising three inlet stages, the first inlet stage is responsive to the speed or number of engine revolutions, the second inlet stage is responsive to the throttle position and includes a retarding circuit and store, and the third inlet stage is responsive to the temperature of the catalyst and includes means for comparing the temperature of the catalyst with a maximum allowable temperature (TMAX.) and a predetermined running temperature (TS). The three inlet stages are electrically coupled to an outlet stage which includes a timer for producing a pulse of predetermined duration.

United States Patent r191 Arrigoni et al.

[ AUTOMATIC DEVICE FOR CONTROLLING CATALYTIC MUFFLERS [75] Inventors:Virgilio Arrigoni, San Donato Milanese; Bruno Gaetani, Milano;Gianfranco Marchesi; Gianfranco Zanoni, both of San Donato Milanese, allof Italy [73] Assignee: Snam Progetti S.p.A., Milan, Italy [22] Filed:Sept. 7, 1972 [21] Appl. No.: 287,009

[30] Foreign Application Priority Data Sept. 10, 1971 Italy 28446/71[52] U.S. Cl 60/277, 60/288, 60/294 [51] Int. Cl. F02b 75/10 [58] Fieldof Search 60/288, 287, 285, 294,

[56] References Cited UNITED STATES PATENTS 3,440,817 4/1969 Saufferer60/288 [451 Sept. 24, 1974 Primary Examiner-Douglas Hart Attorney,Agent, or FirmRalph M. Watson 57 ABSTRACT A device for automaticallycontrolling a by-pass electro-valve of a catalytic muffler comprisingthree inlet stages, the first inlet stage is responsive to the speed ornumber of engine revolutions, the second inlet stage is responsive tothe throttle position and includes a retarding circuit and store, andthe third inlet stage is responsive to the temperature of the catalystand includes means for comparing the temperature of the catalyst with amaximum allowable temperature (T and a predetermined running temperature(T The three inlet stages are electrically coupled to an outlet stagewhich includes a timer for producing a pulse of predetermined duration.

6 Claims, 2 Drawing Figures AUTOMATIC DEVICE FOR CONTROLLING CATALYTICMUFFLERS The present invention relates to a device for the automaticcontrol of catalytic mufflers like the ones used at present time inorder to reduce the outlet of pollutants in exhausts of motor vehicleshaving a controlled ignition. For increasing the life of the mufflercatalyst it is suitable to cut out therein the flow of the gases inthose cases in which said flow would result particularly damaging oruseless, i.e., when the motor presents already a low outlet ofpollutants, this being the case, e.g., at high speeds outside inhabitedplaces, and when a too high temperature occurs in the catalyst due torunning defects.

The cutting out of the gas flow through the catalytic muffler isgenerally obtained by-passing the muffler through a by-pass valveoperated by a control device.

Object of the present invention is to provide a control device allowingthe automatic opening of the by-pass valve once reached determinedconditions of temperature, speed or number of revolutions and throttleopening. Said device according to the invention comprises three stagesresponsive to the vehicle speed or number of revolutions of the engine,to the opening degree of the throttle and to the catalyst temperaturerespectively, and an outlet stage which, controlled by said inletstages, operates a by-pass valve.

According to an essential feature of theinvention the stage responsiveto the opening degree of the throttle delivers a by-pass valve openingsignal to the outlet stage only if the throttle opening keeps higherthan a certain value for a determined time, this being the case, e.g.,for highway runnings; the catalytic muffler is therefore switched on, asnecessary, for full and shorttimed accellerations (city traffic).

According to a further essential feature of the invention the stageresponsive to the catalyst temperature is responsive both to thetemperature gradient as to the time (derivative action), so as tointervene before a destructive temperature T is reached, and to theintegral as to the time of the temperature-rise over the prefixedtemperature T,, so as to prevent the permanence of temperatures which,even if not destructive, will age rapidly the catalyst. Summing up thedevice according to the present invention keeps automatically opened theby-pass valve, cutting out thereby the gas flow through the catalyticmuffler, in the following cases:

when the vehicle speed or the number of revolutions of the engineexceeds a prefixed value, e.g., 50 km/h in third gear;

when the throttle opening exceeds a determined value, e.g., about 80,for a determined period of time, so that the catalytic muffler isswitched on when the full accelerations are short-timed;

when the catalyst temperature exceeds a limit value T beyond which thecatalyst would be damaged, or assumes a gradient as to the time higherthan a prefixed value so as to prevent the reaching of destructive hightemperatures;

when the temperature exceeds for a certain time (integral action) aprefixed value T, whose permanence shortens the catalyst life.

According to a further essential feature of the invention the outletstage of the control device is realized so as to prevent the continuousopening and closing of the by-pass valve when the logical valve openingsignals, coming from the inlet stages, fluctuate around limit values ofintervention. This is practically obtained by exciting with an outletsignal of a gate circuit OR, at the inlet of which there is convergenceof the logical signals coming from the other inlet stages, a retardinglogic consisting of a timer delivering a pulse of controlled duration,and sending the outlet signal of said gate circuit OR and the outletsignal of said timer to the inlet of another gate circuit OR whoseoutlet controls directly the by-pass valve. In this way, even if for anyreason, e.g., fluctuation around the limit values of intervention, thereis no by-pass valve opening signal at the inlet of the first gatecircuit OR," the timer, once excited, keeps on delivering the signal forkeeping opened said by-pass valve for the whole prefixed period of time.

Finally it has to be pointed out that the whole automatic control deviceaccording to the invention may be fed by the vehicle battery or by thenetwork for roller tests.

The invention will be now illustrated with reference to the encloseddrawing showing a preferred form ofpractical realization given only byway of example, since many technical and network variants may be thoughtwithout departing from the scope of the present invention.

FIG. 1 shows schematically in a block diagramm the by-pass of acatalytic muffler through an electro-valve automatically controlled by acontrol electromechanical device according to the invention;

FIG. 2 shows in a block diagramm the circuit schema of the controlelectro-mechanical device of FIG. 1 according to the invention.

With reference to figures, 1 indicates the catalytic muffler to beprotected, 2 indicates the by-pass electro-' valve and 3 the automaticcontrol device. Said automatic control device 3 comprises according tothe in vention three inlet stages responsive to the vehicle speed or thenumber of engine revolutions, to the throttle opening degree and to thecatalyst temperature of the catalytic muffler 1 respectively, and anoutlet stage reached by the logical signals coming from said inletstages and which controls the by-pass valve 2.

The inlet stage responsive to the vehicle speed or the number of enginerevolutions comprises (see FIG. 2) a speedometer dynamo 4 or a deviceindicating the number of the engine revolutions, which delivers avoltage proportional to the engine speed or number of revolutions, thisvoltage being compared in node 5 with a reference voltage set up by apotentiometer 6. The difference between the two said voltages operatesthen a speed level discriminator 7 whose outlet is connected with theOR" gate circuit 8 of the outlet stage. In this way at the outlet ofdiscriminator 7 a valve opening sig nal will appear only'if the voltagedelivered by the speedometer dyamo or by the device indicating thenumber of revolutions is higher than the voltage set up on potentiometer6, i.e., therefore, when the speed or the number of the revolutions ofthe engine exceeds the prefixed value corresponding, e.g., to 50 Km/h inthird gear.

The inlet stage responsive to the throttle opening degree comprises alevel discriminator 9 at the inlet of which one applies the differencebetween the voltage, signal proportional to the position of throttle 10,obtained, e.g., by means of a potentiometer whose slider is rigidlyconnected with the throttle, and the reference voltage set up throughpotentiometer 11.

Here too, therefore, it is possible to have a signal at the outlet ofdiscriminator 9 only if said difference is positive, i.e., if thethrottle opening degree is higher than the set up reference value,corresponding, e.g., to

- 24 releases by-pass valve 2 before T temperature is reached andprevents therefore the reaching of high dea throttle rotation of 80.This discriminator outlet signal is not however directly sent to OR gatecircuit 8 of the outlet stage, but is applied at the same time to aretarding circuit 12, delivering a pulse after a prefixed period oftime, and to an AND type circuit 13 reached too by the retarding pulse.The AND circuit outlet excites then a store 14 whose outlet is directlyconnected with said OR gate circuit of the outlet stage. In this way,store 14 will deliver to the outlet stage a valve opening signal notwhen there is a signal at the outlet of discriminator 9, i.e., when thethrottle opening exceeds a certain prefixed level, but only when thethrottle opening keeps higher than said level for a period of time atleast corresponding to the delay time of retarding circuit 12. In factAND gate circuit 13 opens and excites store 14 only when there are atits inlet both signals and therefore, even if there is the outlet signalof discriminator 9 but its duration is lower than the one required byretarding circuit 12 to give its pulse, AND circuit 13 does not open. Itis possible in this way to prevent that by-pass valve 2 opens in case offull accellerations having a short duration, e.g., ac-

cellerations occurring at the changing of gears (city traffic).

The presence of store 14 is then necessary since the outlet signal ofAND circuit 13 is a short-timed pulse whereas the valve opening signalmust be a signal keeping on till the throttle opening has gone under theprefixed level. Store 14, comprising a series of flip-flop or NORcircuits, has indeed the dutyv of storing and transforming the excitingpulse at its inlet into a continuous signal at its outlet and of keepingthis signal till at the outlet of discriminator 9 there is a signal.When there is no more this latter signal, since the throttle opening hasgone under the prefixed level, store 14 is set to zero by the sameoutlet signal of discriminator 9 inverted by inverter 15.

In FIG. 2 it has been shown too indicator 16 by means of which it ispossible to visualize the value of the speed or of the number of enginerevolutions and the throttle opening degree.

The third inlet stage responsive to the catalyst temperature ofcatalytic muffler l is, on the contrary, constituted by a thermoelement17 whose voltage signal, proportional to said temperature, is amplifiedby means of operational amplifier l8 and visualized by indicating device19. The outlet signal of amplifier 18 is then differentiated by means ofdifferentiating RC circuit, comprising resistance 20 and capacitor21,and then compared in node 22 with the reference signal to be prefixed onpretentiometer 23 and corresonding to the limit destructive temperatureT e.g., 800C. The resulting difference signal is then sent to a leveldiscriminator 24 whose outlet is connected with said OR gate I circuitof the outlet stage. In this way in node 22 there is only a signal whichis the sum of the signal proportional to the temperature and of its.derivative as to the time and therefore the discriminator 24 delivers avalve opening signal at its outlet not when the catalyst temperaturereaches T value, but when this value is reached by said sum signal.Summing up discriminator structive temperatures. On the other side thesignal of thermoelement l7, amplified by operational amplifier 18, iscompared too in node 25 with a reference signal, delivered bypotentiometer 26. proportional to a certain running temperature "1",,e.g., 500C, a catalyst temperature-rise as to the latter being notdestructive but at the long run shortening the catalyst life.

The temperature-rise signal resulting in node 25 is then sent, at thesame time, to a terminal of a relay 27 and to the inlet of a mean leveldiscriminator 28 whose outlet, exciting the above mentioned relay,switches on the same signal on the outlet of an integrator 29 which,integrating this temperature-rise signal, will take a time proportionalto the magnitude of this signal for reaching the integral thresholdlevel T predetermined by potentiometer 30. The reaching of the integralthreshold limit T this meaning that the temperature-rise as to therunning temperature lasts for a certain period of time and is thereforeharmful for the catalyst of the catalytic muffler, is detected by leveldiscriminator 31 which excites store 32 whose outlet is connected withsaid OR gate circuit 8 of the outlet stage.

Said store 32 is like and has the same function of store 14 alreadycited and, like the latter, is set to zero by the outlet signal ofdiscriminator 28 inverted by inverter 33.

By means of this latter part of the device circuit it is possibletherefore to send to the outlet stage a valve opening signal every timethat the catalyst temperature exceeds a certain critical value T, whoselasting, harmful for the catalyst, allows the outlet of integrator 29 toreach the integral threshold value T P16. 2 visualizes too potentiometer37 for calibrating operational amplifier 18.

Finally the outlet stage of the device according to the inventioncomprises the already cited OR gate circuit 8 reached by the logicalvalve opening signals coming from the inlet stages, whose outlet excitesa timer 34 capable of delivering a pulse of duration to be prefixed.Said duration-prefixed pulse, produced by timer 34 once excited, is senttogether with the outlet signal of OR gate circuit 8 to the inlet ofanother OR" gate circuit 35 whose outlet 36 operates directly bypasselectro-valve 2.

In this way by-pass valve 2 keeps opened not only when there is a singlelogical signal at the inlet of OR gate circuit 8, but keeps opened evenif said logical signal disappears because, e.g., of its fluctuationaround its limit value of intervention. ln fact, timer 34, once excited,keeps on delivering a valve opening signal for the whole period of timetherein prefixed.

What we claim is:

1. An automatic control device for controlling a bypass electro-valve inan arrangement comprising an engine having a throttle and an exhaustsystem, said exhaust system having a catalytic muffler containing acatalyst and a by-pass duct, around said muffler, containing saidby-pass electro-valve, comprising:

three inlet stages;

said first inlet stage being responsive to the speed or number ofrevolutions of the engine;

said second inlet stage being responsive to the position of thethrottle, including a level discriminator for receiving at its input adifference voltage including a voltage proportional to the position ofthe throttle and a reference voltage, retarding circuit electricallycoupled to said level discriminator for producing an output pulse aftera predetermined time in response to an output signal from said leveldiscriminator, coincident gate means electrically coupled to the outputof said level discriminator and said retarding circuit to produce anoutput signal in response to signals from said level discriminator andsaid retarding circuit, a store electrically coupled to the output ofsaid coincident gate means;

said third inlet stage being response to the temperature of thecatalyst; and

an outlet stage for actuating the by-pass electro-valve in response tosignals from said inlet stages.

2. An automatic control device as claimed in claim 1 wherein:

said store includes a plurality of flip-flops or NOR gates;

an inverter also electrically couples the output of said leveldiscriminator directly to said store to set the output signal from saidstore to zero in the absence of an output signal from said coincidentgate means.

3. An automatic control device for controlling a bypass electro-valve inan arrangement comprising an engine having a throttle and an exhaustsystem, said exhaust system having a catalytic muffler containing acatalyst and a by-pass duct, around said muffler, containing saidby-pass electro-valve, comprising:

three inlet stages;

said first inlet stage being responsive to the speed or number ofrevolutions of the engine;

said second inlet stage being responsive to the position of thethrottle;

said third inlet stage being responsive to the temperature of thecatalyst, including thermoelement means for providing an output signalproportional to the temperature of the catalyst, an operationalamplifier electrically coupled to said thermoelement, differentiatingcircuit means electrically coupled to the output of said operationalamplifier, potentiometer means for providing a reference signalcorresponding to a maximum temperature limit (T a level discriminatorelectrically coupled to said potentiometer means and saiddifferentiating circuit means for receiving at its input a differencesignal; and

an outlet stage for actuating the by-pass electro-valve in response tosignals from said inlet stages.

4. An automatic control device as claimed in claim 3 including:

second potentiometer means electrically coupled to the output of saidoperational amplifier to provide a reference signal corresponding to apredetermined running temperature (T a relay having one of its terminalselectrically coua second level discriminator also electrically coupledto the output of said operational amplifier to actuate said relay;

an integrator electrically coupled to another terminal of said relay,said integrator providing an output signal in response to actuation ofsaid relay by said second level discriminator;

third potentiometer means electrically coupled to the output of saidintegrator to provide a reference signal corresponding to an integralthreshold temperature limit (T,);

a third level discriminator electrically coupled to the output of saidintegrator and said third potentiometer means; and

a store electrically coupled to the output of said third leveldiscriminator.

5. An automatic control device as claimed in claim 4 wherein:

said store includes a plurality of flip-flops or NOR" gates;

an inverter also electrically couples the output of said second leveldiscriminator to said store to set the output signal from said store tozero in the absence of an output signal from said third leveldiscriminator.

6. An automatic control device for controlling a bypass electro-valve inan arrangement comprising an engine having a throttle and an exhaustsystem, said exhaust system having a catalytic muffler containing acatalyst and a by-pass duct, around said muffler, containing saidby-pass electro-valve, comprising:

three inlet stages;

said first inlet stage being responsive to the speed or number ofrevolutions of the engine;

said second inlet stage being responsive to the position of thethrottle;

said third inlet stage being responsive to the temperature of thecatalyst; and

an outlet stage including a first OR gate to receive the output signalsfrom said inlet stages, a second OR gate having a first input terminalelectrically coupled to the output of said first OR gate, a timerelectrically coupled to the output of said first OR" gate and to asecond input terminal of said second OR gate, said timer producing anoutput pulse of predetermined duration in response to an output signalfrom said first OR gate, the output from said second OR gate directlycontrolling the by-pass electro-valve.

1. An automatic control device for controlling a by-pass electro-valvein an arrangement comprising an engine having a throttle and an exhaustsystem, said exhaust system having a catalytic muffler containing acatalyst and a by-pass duct, around said muffler, containing saidby-pass electro-valve, comprising: three inlet stages; said first inletstage being responsive to the speed or number of revolutions of theengine; said second inlet stage being responsive to the position of thethrottle, including a level discriminator for receiving at its input adifference voltage including a voltage proportional to the position ofthe throttle and a reference voltage, retarding circuit electricallycoupled to said level discriminator for producing an output pulse aftera predetermined time in response to an output signal from said leveldiscriminator, coincident gate means electrically coupled to the outputof said level discriminator and said retarding circuit to produce anoutput signal in response to signals from said level discriminator andsaid retarding circuit, a store electrically coupled to the output ofsaid coincident gate means; Said third inlet stage being response to thetemperature of the catalyst; and an outlet stage for actuating theby-pass electro-valve in response to signals from said inlet stages. 2.An automatic control device as claimed in claim 1 wherein: said storeincludes a plurality of flip-flops or ''''NOR'''' gates; an inverteralso electrically couples the output of said level discriminatordirectly to said store to set the output signal from said store to zeroin the absence of an output signal from said coincident gate means. 3.An automatic control device for controlling a by-pass electro-valve inan arrangement comprising an engine having a throttle and an exhaustsystem, said exhaust system having a catalytic muffler containing acatalyst and a by-pass duct, around said muffler, containing saidby-pass electro-valve, comprising: three inlet stages; said first inletstage being responsive to the speed or number of revolutions of theengine; said second inlet stage being responsive to the position of thethrottle; said third inlet stage being responsive to the temperature ofthe catalyst, including thermoelement means for providing an outputsignal proportional to the temperature of the catalyst, an operationalamplifier electrically coupled to said thermoelement, differentiatingcircuit means electrically coupled to the output of said operationalamplifier, potentiometer means for providing a reference signalcorresponding to a maximum temperature limit (TMAX), a leveldiscriminator electrically coupled to said potentiometer means and saiddifferentiating circuit means for receiving at its input a differencesignal; and an outlet stage for actuating the by-pass electro-valve inresponse to signals from said inlet stages.
 4. An automatic controldevice as claimed in claim 3 including: second potentiometer meanselectrically coupled to the output of said operational amplifier toprovide a reference signal corresponding to a predetermined runningtemperature (TS); a relay having one of its terminals electricallycoupled to the output of said operational amplifier to receive adifference signal representing the sum of output of said operationalamplifier and the reference signal from said second potentiometer means;a second level discriminator also electrically coupled to the output ofsaid operational amplifier to actuate said relay; an integratorelectrically coupled to another terminal of said relay, said integratorproviding an output signal in response to actuation of said relay bysaid second level discriminator; third potentiometer means electricallycoupled to the output of said integrator to provide a reference signalcorresponding to an integral threshold temperature limit (TI); a thirdlevel discriminator electrically coupled to the output of saidintegrator and said third potentiometer means; and a store electricallycoupled to the output of said third level discriminator.
 5. An automaticcontrol device as claimed in claim 4 wherein: said store includes aplurality of flip-flops or ''''NOR'''' gates; an inverter alsoelectrically couples the output of said second level discriminator tosaid store to set the output signal from said store to zero in theabsence of an output signal from said third level discriminator.
 6. Anautomatic control device for controlling a by-pass electro-valve in anarrangement comprising an engine having a throttle and an exhaustsystem, said exhaust system having a catalytic muffler containing acatalyst and a by-pass duct, around said muffler, containing saidby-pass electro-valve, comprising: three inlet stages; said first inletstage being responsive to the speed or number of revolutions of theengine; said second inlet stage being responsive to the position of thethrottle; said third inlet stage being responsive to the temperature ofthe catalyst; and an outlet stage including a First ''''OR'''' gate toreceive the output signals from said inlet stages, a second ''''OR''''gate having a first input terminal electrically coupled to the output ofsaid first ''''OR'''' gate, a timer electrically coupled to the outputof said first ''''OR'''' gate and to a second input terminal of saidsecond ''''OR'''' gate, said timer producing an output pulse ofpredetermined duration in response to an output signal from said first''''OR'''' gate, the output from said second ''''OR'''' gate directlycontrolling the by-pass electro-valve.